Cell-substrate adhesion of cells derived from mouse mammary carcinomas and normal glands has been assessed by a variety of detachment assays including ease of trypsinization and ease of removal with divalent cation chelators. Some tumor-derived cells were always easier to detach than normal cells, whereas other tumor-derived cells were initially more difficult to detach but became easier to detach with time. This latter pattern may be of significance in metastasis; hence, matrix composition, elaboration and degradation of matrix components and the effect on adhesion of alterations in matrix and surface membrane components, e.g., the previously observed glycosylation changes, are currently under study.